Numerical solution of shallow-water equations （SWE） has been a challenging task because of its nonlinear hyperbolic nature, admitting discontinuous solution, and the need to satisfy the C-property. The presence of s...Numerical solution of shallow-water equations （SWE） has been a challenging task because of its nonlinear hyperbolic nature, admitting discontinuous solution, and the need to satisfy the C-property. The presence of source terms in momentum equations, such as the bottom slope and friction of bed, compounds the difficulties further. In this paper, a least-squares finite-element method for the space discretization and θ-method for the time integration is developed for the 2D non-conservative SWE including the source terms. Advantages of the method include： the source terms can be approximated easily with interpolation functions, no upwind scheme is needed, as well as the resulting system equations is symmetric and positive-definite, therefore, can be solved efficiently with the conjugate gradient method. The method is applied to steady and unsteady flows, subcritical and transcritical flow over a bump, 1D and 2D circular dam-break, wave past a circular cylinder, as well as wave past a hump. Computed results show good C-property, conservation property and compare well with exact solutions and other numerical results for flows with weak and mild gradient changes, but lead to inaccurate predictions for flows with strong gradient changes and discontinuities.展开更多
An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in ...An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in all the orbital elements with the present theory over second-order theory. The theory is used for computing the mean orbital elements, which are found to be more accurate than provided by Bhatnagar and taqvi’s theory (up to second power in eccentricity). Mean elements have a large number of practical applications.展开更多
An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new s...An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.展开更多
English and Chinese address terms have apparent differences,which are caused by their own different social and cultural backgrounds and reflect different cultural implications between the east and the west. To underst...English and Chinese address terms have apparent differences,which are caused by their own different social and cultural backgrounds and reflect different cultural implications between the east and the west. To understand the eastern and western culture better,it's necessary to make a comparison between them.展开更多
Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerabl...Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.展开更多
篇章要素识别(discourse element identification)的主要任务是识别篇章要素单元并进行分类.针对篇章要素识别对上下文依赖性理解不足的问题,提出一种基于BiLSTM-Attention的识别篇章要素模型,提高议论文篇章要素识别的准确率.该模型利...篇章要素识别(discourse element identification)的主要任务是识别篇章要素单元并进行分类.针对篇章要素识别对上下文依赖性理解不足的问题,提出一种基于BiLSTM-Attention的识别篇章要素模型,提高议论文篇章要素识别的准确率.该模型利用句子结构和位置编码来识别句子的成分关系,通过双向长短期记忆网络(bidirectional long short-term memory,BiLSTM)进一步获得深层次上下文相关联的信息;引入注意力机制(attention mechanism)优化模型特征向量,提高文本分类的准确度;最终用句间多头自注意力(multi-head self-attention)获取句子在内容和结构上的关系,弥补距离较远的句子依赖问题.相比于HBiLSTM、BERT等基线模型,在相同参数、相同实验条件下,中文数据集和英文数据集上准确率分别提升1.3%、3.6%,验证了该模型在篇章要素识别任务中的有效性.展开更多
语篇要素识别在自动作文评分中发挥着重要作用,提高语篇要素识别的准确率有助于增强自动作文评分的效果以及可解释性。然而,语篇要素识别任务面临着上下文依赖和句子歧义性等挑战。传统的基于规则和特征工程的方法难以捕捉文本中复杂的...语篇要素识别在自动作文评分中发挥着重要作用,提高语篇要素识别的准确率有助于增强自动作文评分的效果以及可解释性。然而,语篇要素识别任务面临着上下文依赖和句子歧义性等挑战。传统的基于规则和特征工程的方法难以捕捉文本中复杂的语义信息和长距离依赖关系,而深度学习方法虽然能够自动学习文本特征,但仍然存在对关键位置信息利用不足的问题。针对上述问题,提出了一种混合位置编码的语篇要素识别模型,即HPE-BiLSTM(Hybrid Position Encoding Bidirectional Long Short-Term Memory)。该模型首先基于预训练的词向量获取句子表示,然后通过双向长短期记忆网络提取句子级特征。在句子级特征的基础上,采用混合的位置编码方案以确保关键位置信息的有效传递。最后,使用线性层和激活函数实现语篇要素识别。该模型在议论文数据集进行实验,并与Feature-based、BERT、BiLSTM、DiSA和DCRGNN五个模型进行比较。实验结果表明,HPE-BiLSTM模型的准确率达到了0.693,在语篇要素识别方面的F 1分数为0.684,优于其他模型。展开更多
岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性...岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性。长短期记忆(long short-term mernory,简称LSTM)深度学习算法适用于处理具有时间序列的数据任务,用于预测岩石短长期力学特性具有显著优势。通过引入LSTM算法,分别根据三轴压缩加载路径和应力松弛随时间变化的规律构建序列数据,建立了灰砂岩在常规三轴压缩以及应力松弛下的力学特性预测模型。与试验数据进行对比,可以证明基于深度学习的岩石短长期力学预测本构模型的准确性。为进一步提升模型工程应用价值,将LSTM本构模型嵌入到有限元法(finite element method,简称FEM)框架中进行数值实现,并应用于灰砂岩变形特性的模拟。对比结果表明,LSTM-FEM方法具有较好地预测岩石短长期变形特性的能力。展开更多
基金the National Science Council of Taiwan for funding this research (NSC 96-2221-E-019-061).
文摘Numerical solution of shallow-water equations （SWE） has been a challenging task because of its nonlinear hyperbolic nature, admitting discontinuous solution, and the need to satisfy the C-property. The presence of source terms in momentum equations, such as the bottom slope and friction of bed, compounds the difficulties further. In this paper, a least-squares finite-element method for the space discretization and θ-method for the time integration is developed for the 2D non-conservative SWE including the source terms. Advantages of the method include： the source terms can be approximated easily with interpolation functions, no upwind scheme is needed, as well as the resulting system equations is symmetric and positive-definite, therefore, can be solved efficiently with the conjugate gradient method. The method is applied to steady and unsteady flows, subcritical and transcritical flow over a bump, 1D and 2D circular dam-break, wave past a circular cylinder, as well as wave past a hump. Computed results show good C-property, conservation property and compare well with exact solutions and other numerical results for flows with weak and mild gradient changes, but lead to inaccurate predictions for flows with strong gradient changes and discontinuities.
文摘An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in all the orbital elements with the present theory over second-order theory. The theory is used for computing the mean orbital elements, which are found to be more accurate than provided by Bhatnagar and taqvi’s theory (up to second power in eccentricity). Mean elements have a large number of practical applications.
文摘An analysis of a 3 dB lumped-element directional coupler （LEDC） based on arbitrary terminal impedance is described numerically. To solve the conflicted requirement for broad bandwidth and small size in LEDC, a new structure of coupler is introduced, which can significantly improve bandwidth and whose size is only 3 cm×4 cm on the conditions of the frequency domain of 410 MHz to 490 MHz. The measure results are in good agreement with simulations despite the unexpected resistor loss.
文摘English and Chinese address terms have apparent differences,which are caused by their own different social and cultural backgrounds and reflect different cultural implications between the east and the west. To understand the eastern and western culture better,it's necessary to make a comparison between them.
基金supported by 973 Program of China under Grant No.2006CB302900part by the National Natural Science Foundation of China under Grant No.60825405 and No.60778018
文摘Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.
文摘篇章要素识别(discourse element identification)的主要任务是识别篇章要素单元并进行分类.针对篇章要素识别对上下文依赖性理解不足的问题,提出一种基于BiLSTM-Attention的识别篇章要素模型,提高议论文篇章要素识别的准确率.该模型利用句子结构和位置编码来识别句子的成分关系,通过双向长短期记忆网络(bidirectional long short-term memory,BiLSTM)进一步获得深层次上下文相关联的信息;引入注意力机制(attention mechanism)优化模型特征向量,提高文本分类的准确度;最终用句间多头自注意力(multi-head self-attention)获取句子在内容和结构上的关系,弥补距离较远的句子依赖问题.相比于HBiLSTM、BERT等基线模型,在相同参数、相同实验条件下,中文数据集和英文数据集上准确率分别提升1.3%、3.6%,验证了该模型在篇章要素识别任务中的有效性.
文摘语篇要素识别在自动作文评分中发挥着重要作用,提高语篇要素识别的准确率有助于增强自动作文评分的效果以及可解释性。然而,语篇要素识别任务面临着上下文依赖和句子歧义性等挑战。传统的基于规则和特征工程的方法难以捕捉文本中复杂的语义信息和长距离依赖关系,而深度学习方法虽然能够自动学习文本特征,但仍然存在对关键位置信息利用不足的问题。针对上述问题,提出了一种混合位置编码的语篇要素识别模型,即HPE-BiLSTM(Hybrid Position Encoding Bidirectional Long Short-Term Memory)。该模型首先基于预训练的词向量获取句子表示,然后通过双向长短期记忆网络提取句子级特征。在句子级特征的基础上,采用混合的位置编码方案以确保关键位置信息的有效传递。最后,使用线性层和激活函数实现语篇要素识别。该模型在议论文数据集进行实验,并与Feature-based、BERT、BiLSTM、DiSA和DCRGNN五个模型进行比较。实验结果表明,HPE-BiLSTM模型的准确率达到了0.693,在语篇要素识别方面的F 1分数为0.684,优于其他模型。
文摘岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性。长短期记忆(long short-term mernory,简称LSTM)深度学习算法适用于处理具有时间序列的数据任务,用于预测岩石短长期力学特性具有显著优势。通过引入LSTM算法,分别根据三轴压缩加载路径和应力松弛随时间变化的规律构建序列数据,建立了灰砂岩在常规三轴压缩以及应力松弛下的力学特性预测模型。与试验数据进行对比,可以证明基于深度学习的岩石短长期力学预测本构模型的准确性。为进一步提升模型工程应用价值,将LSTM本构模型嵌入到有限元法(finite element method,简称FEM)框架中进行数值实现,并应用于灰砂岩变形特性的模拟。对比结果表明,LSTM-FEM方法具有较好地预测岩石短长期变形特性的能力。
